1. Field of the Invention
The present invention relates to a coated cutting tool insert designed to be used in fine to medium-rough turning stainless steels. The substrate is cemented carbide on which a hard and wear resistant coating is deposited. The said coating is composed of one or more refractory layers of which at least one layer is a strongly textured (006) alpha-alumina (α-Al2O3).
2. Description of the Related Art
Steels are said to be stainless when they resist corrosion, or more properly when they are highly resistant to corrosion. The resistance to corrosion is achieved through dissolving sufficient chromium in the iron to produce a coherent, adherent, and regenerating chromium oxide protective film on the surface. A concentration of at least 11 wt-% Cr is required. Most of the stainless steels are based on the Fe—Cr—C and Fe—Cr—Ni—C systems, but other alloying elements are also important.
Stainless steels are used in harsh environments where high corrosion resistance is needed. Some stainless steels are also frequently used at elevated temperatures in severe environments due to their resistance to corrosion and the fact that they maintain their mechanical strength even at elevated temperatures. Stainless steels are among others used in automotive components, for chemical and food processing equipment, for surgical instruments and for cutlery and knives, where both aesthetic appearance and corrosion resistance are important design criteria.
When machining stainless steels toughness and wear resistance are important properties of the cutting tool. A tougher cutting tool will reduce the risk for chip hammering, chipping and notching. Wear resistance is needed to reduce the risk for plastic deformation, as the temperatures of the cutting edge will be high, a consequence of the poor heat conductivity of stainless steels. The wear resistance will also reduce abrasive wear, which will occur from hard aluminium oxide or carbide inclusions in the stainless steel as well as from work hardened surfaces created in previous cuts.